Knee orthosis
BACKGROUND OF THE DISCLOSURE 
     The field of the invention is medical appliances, and the invention relates more particularly to orthotics. The invention relates still more particularly to knee braces of the type useful for athletes and post-op, post-injury patients, particularly those with damaged anterior cruciate ligament (ACL) injury. 
     Many new post-injury knee orthoses have appeared on the market, and many such braces have found widespread use and have enabled the users to prevent further knee injury. The effectiveness of such knee braces differs widely, however, and factors such as comfort, stability, restrictiveness, suspension, weight, appearance, durability, price availability and service are all factors which must be considered. Even the most scientifically designed brace will be of no benefit if the patient dislikes wearing it, or if it is very time consuming to secure. 
     A pair of related patents have recently issued showing a knee brace of the general type discussed below, namely, U.S. Pat. Nos. 4,723,539 and 4,773,404. Under load and at a 30° s of flexion, however, there is eight millimeters of anterior draw in the hinge alone. It has been found that such hinge permits excessive translocation of the tibia by following the motion of the tibia rather than by guiding it. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a light-weight, comfortable, durable and stable hinge which tends to initiate a posteriorly directed force on the tibia as it begins to flex, thereby guiding the tibia in a motion which keeps it in its proper position. 
     The present invention is for an improved knee orthosis of the type having a femoral shell having a medial femoral upright and a lateral femoral upright affixed thereto, a tibial shell having a medial tibial upright and a lateral tibial upright affixed thereto, and means for hinging the medial uprights together and means for hinging the lateral uprights together, together with straps to hold the shells in place. The improvement of the present invention comprises a medial hinge and a lateral hinge, each of said hinges having a pair of femoral pins comprising an anterior femoral pin and a posterior femoral pin. The pair of femoral pins are affixed to the femoral upright near the base thereof. A pair of tibial pins comprising an anterior tibial pin and a posterior tibial pin, said pair of tibial pins being affixed to said tibial upright near the top thereof. A first link plate is affixed to said anterior femoral pin and to said anterior tibial pin, and a second link plate is affixed to said posterior femoral pin and to said posterior tibial pin. The femoral upright and the tibial upright are co-planar. The present invention further includes an improved tibial shell which has a C-shaped portion to which the tibial uprights are attached and which extends over the anterior of the tibia. A spiral portion extends downwardly and spirally from one end of the C-shaped portion subtending at least 180° from the hinge from which it extends. Preferably, the pair of femoral pins are oriented about horizontally when the femoral upright is vertical, and the pair of tibial pins is also oriented about horizontally when the tibial upright is vertical. Also, the rotational movement is preferably limited by contact between the base of the femoral upright and the top of the tibial upright. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the knee brace of the present invention strapped to the right knee of a patient. 
     FIG. 2A is a side view of the medial hinge of the knee brace of FIG. 1 showing an initial deflection of the tibial upright in phantom view. 
     FIG. 2B is a side view of the medial hinge of FIG. 2A showing progressive movement of the femoral upright and the tibial upright. 
     FIG. 2C is a side view of the medial hinge of FIG. 2A showing progressive movement of the femoral upright and the tibial upright. 
     FIG. 2D is a side view of the medial hinge of FIG. 2A showing progressive movement of the uprights in their maximum flexure position. 
     FIG. 3 is a front view of the hinge of FIG. 2. 
     FIG. 4 is a reverse side view of the hinge between the medial femoral upright and medial tibial upright showing the opposite side as that shown in FIG. 2. 
     FIG. 5 is a perspective view of the left side of the knee brace of FIG. 1. 
     FIG. 6 is a front view thereof. 
     FIG. 7 is a rear view thereof. 
     FIG. 8 is a left side view thereof. 
     FIG. 9 is a cross-sectional view taken along line 9--9 of FIG. 8. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The knee brace of the present invention is shown in FIG. 1 and indicated generally be reference character 10. Brace 10 is strapped about the right leg 11 of the wearer. Brace 10 has a femoral shell 12 strapped about the thigh 13 of the wearer, and a tibial shell 14 strapped about the calf and tibia 15 of the wearer. 
     Attempts at duplicating the complex kinematics of the knee with external mechanisms have been, if anything, mildly successful. The primary function of any knee orthosis should be the control of anterior tibial excursion. Without stabilization of this motion, loads placed on the anterior cruciate ligament and secondary structures of the knee are greatly increased. The need for a mechanically correct hinge is crucial before attempting to brace the anterior cruciate ligament deficient knee. Upon close examination, geared polycentric and single access hinges encourage anterior tibial excursion as the knee flexes. The hinge of the present invention more closely approximates the kinematics necessary to stabilize the anterior cruciate ligament deficient knee because the hinge of the present invention provides for posterial tibial shift without a tendency toward shear while in flexion. Each knee brace has a lateral hinge 16 which includes a lateral femoral upright 17 and a lateral tibial upright 18. Medial hinge 19 similarly has a medial femoral upright 20 and a medial tibial upright 21. The medial hinge 19 is shown in detail in FIGS. 2, 3 and 4. The lateral hinge 16 would be a mirror image of the medial hinge. 
     As shown in FIG. 2A medial hinge 19 has a medial femoral upright 20 which includes a pair of femoral pins, namely, a posterior femoral pin 22 and an anterior femoral pin 23. Anterior femoral pin 23 also passes through an inner link 24. Inner link 24 is preferably circular and is also connected to an anterior tibial pin 25. Anterior tibial pin 25 also passes through the medial tibial upright 21 near the top thereof. 
     Posterior femoral pin 22 passes through an outer disk 26 shown best in FIG. 4. A posterior tibial pin 27 is rotatingly connected to outer link 26 as well as to the upper portion of medial tibial upright 21. The link is shown in front view in FIG. 3 where it can be seen that the medial femoral upright 20 is aligned with the medial tibial upright 21. 
     The unique motion of the hinges of the present invention is shown best in FIGS. 2A through 2D. In the upright position, shown in FIG. 2A, it can be seen that the bottom 28 of the femoral upright 20 contacts the top 29 of the tibial upright 21 at points 30 and 31. Similarly, as the hinge is flexed, as shown in FIG. 2D, the top 29 of tibial upright 21 contacts the femoral upright at a point indicated at reference character 32. This, of course, stops further flexure. 
     Most importantly, it can be seen by the phantom view in FIG. 2A that the tibia is urged rearwardly at the initiation of flexure. This prevents a subluxing forward of the tibia which is the most common disfunction of the anterior cruciate ligament deficient knee. 
     It can be seen in FIG. 2A that when the femoral and tibial uprights are in their position of maximum extension that the anterior femoral pin 23, the posterior tibial pin 27 and the anterior tibial pin 25 form about an equilateral triangle. It can also be seen that the pair of femoral pins 22 and 23 are about horizontal as are the pair of tibial pins 25 and 27. By this positioning, it has been found that the links securely support and guide the movement of the two uprights in a particularly desirable motion. It is also noted that inner link 24 goes through a lesser rotary movement than does outer link 26. Thus, it is preferable, although not essential, that the inner link be placed on the inner surface of the hinge. It should also be noted that both of the femoral pins 22 and 23 are behind the central axis 20&#39; of the femoral upright and that the tibial pins are on opposite sides of the central axis 21&#39; of the tibial upright 21. Preferably, the femoral pins are about 9/16ths of an inch apart and the tibial pins are about  1 and 1/16th inches apart. Furthermore, preferably, the femoral pins are about 11/8 th inches above the tibial pins. 
     The constructions of the femoral and especially the tibial shell 12 and 14 form another important feature of the present invention. These are shown best in FIGS. 5 through 9. A right side view of the hinge of the present invention is shown in FIG. 5. Femoral shell 12 and tibial shell 14 are preferably fabricated from a thermoplastic polymer so that they may be vacuum formed. This provides both a lightweight, strong and aesthetically attractive material. High density polyethylene has been found effective for this purpose. The hinge material is preferably fabricated from high tensile strength aircraft aluminum, and this is preferably covered with a sponge pad both for aesthetics as to the outer link and for comfort as to the inner link. Likewise, the shells are laminated with a sponge material for comfort and also to assist in holding the shells in place. 
     In FIG. 5, it can be seen that femoral shell 12 is securable to the wearer by a lower strap 35 which is affixed by a conventional buckle 36 riveted to shell 12. Lower strap 35 is advantageously secured with Velcro type of attachment. A wide upper strap 37 is preferably made from an elastic material so that it may give with the flexure of the quadrilateral muscles and the hamstring muscles. Strap 37 is, likewise, preferably secured to shell 12 by Velcro, portions of which are indicated by reference characters 37&#39;  and 37&#34;. This is preferably obtained by the affixing of a layer of hook material 38 to the side of shell 12 and then providing a wide elastic strap 37 which has pile material 37&#39; at one end for connection to hook material 38 and hook material 37&#34; at the other end for connection to the exterior of strap 37, itself. 
     Lower shell 14 has a spiral design which is indicated generally by reference character 40. Shell 14 has a C-shaped portion 41 to which an upper strap 42 is held through loop 43. The spiral portion extends downwardly and circularly around the calf region of the wearer and terminates at its lower end 44. A rectangle of hook material 45 is affixed near the terminus 44 of spiral 40. A lower elastic strap 46 has a section of pile material 46&#39; for affixing to hook material 45. The strap is then wound around the calf and, as with strap 37, has a layer of hook material 46&#34; at its outer end which is attachable to the outer surface of strap 46. This spiral construction assists in securing the tibia against anterior tibial excursion. It is also easy to affix over the tibia since it is capable of flexing, as shown by phantom line 47, whereby the ankle can be easily passed through the space between the lower part of the spiral and the C-shaped portion of shell 14. As shown in FIG. 9, it can be seen that the spiral extends more than 360°  from its point of beginning indicated by reference character 48. 
     The knee orthosis of the present invention is especially comfortable and this helps assure patient compliance. It is attractive in appearance because of its smooth, modern lines and the novel hinge construction. It withstands the rigors of today&#39;s athlete and is quickly applied and removed. 
     The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.